The present invention relates to a method and a device for ensuring storage time for digital broadcast that can ensure recording time required when a digital broadcast compressed by MPEG or the like is stored and recorded in a recording medium such as an optical disk, an optomagnetic disk or a hard disk.
Recently, in accordance with improvement of image signal processing techniques, a record-and-playback device for recording in a disk-shaped storage medium that is capable of freely recording/playing back a video or voice digital signal, such as a DVD-RAM or a hard disk has been developed.
As a method for storing and recording analog broadcast data in such a storage medium, for example, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 8-17137, there has been known a method that a target bit-rate is calculated on the basis of the storage capacity of the storage medium and a predetermined recording time and then the data is encoded so as to be contained in the storage medium. Namely, because the recording capacity for the storage medium and the recording time for an analog broadcast to be stored are known, a bit-rate can be determined by the expression, recording capacity÷recording time. Then, control is performed so that the analog broadcast is compressed and recorded at this resultant bit-rate.
In the case of storing and recording not analog broadcast data but digital broadcast data, however, sources for the digital broadcast are for a standard television in current CS broadcasting performed in Japan. In BS digital broadcasting, a standard television and high-definition television are supported. Further, even in the same standard television or high-definition television, a bit-rate of broadcast is different for each program. In ground wave digital broadcasting that will be started in 2003 or later, a standard television, a high-definition television and a level lower than MPEG4 Simple Profile Level 3 will be provided. In accordance with MPEG4 Simple Profile Level 3, an image size is CIF (¼ of current vertical and horizontal sizes, respectively) and a bit-rate is equal to or less than 384 kbit/s. Thus, when these three kinds of broadcasts are stored and recorded in a digital form, a storage time may be varied for each of the bit-rates for these broadcasts even in the case of storing the same broadcast program, unlike a conventional analog VHS VTR which can simply define the storage time in a 120 min tape as two hours in a standard mode and six hours in a triple-mode. Accordingly, a problem exists in the method for ensuring a storing and recording time.